1. Field of the Invention
With regard to the classification of art, this invention is believed to be found in the general class entitled Package Making and more particularly to those subclasses pertaining to the seating of a lid on a pre-formed container by means of a lid press.
2. Description of Related Art
Pre-formed containers such as molded pails, buckets and the like are used in the distribution of various products. These containers require a lid to be seated or secured thereto after a filling operation, in a processing plant.
Usually the lids are placed on the pre-formed container by a lid placing apparatus similar to U.S. Pat. No. 4,959,944, that issued to Heisler on Oct. 2, 1990, or U.S. Pat. No. 5,050,367, that issued to Heisler on Sep. 24, 1991. These patents, cited above, are illustrative of apparatus and methods for placing a lid on a pre-formed container. Each of the cited patents employ a roller compression system for seating the lids after placement. It has been found that the roller compression system may not meet the industry requirements for applying certain lids onto containers containing products that may need to be burped to reduce trapped air.
U.S. Pat. No. 5,438,814, that issued to Lovett et al on Aug. 8, 1995, attempted to address the seating of a lid on a continuously conveyed pre-formed container. However it has been found that the solution that was proposed by Lovett in U.S. Pat. No. 5,438,814 may not provide reliable results under actual manufacturing conditions. In order for the Lovett apparatus to function properly, the horizontal movement of the lid press plate must exactly match the velocity of the continually moving conveyor carrying the pre-formed container. However, it has been found that tipping of the container may occur when there is any variation between the velocity of the lid press plate and the container using the Lovett apparatus. Any tipping or jostling of the filled container prior to the full seating of the lid results in spillage of the product onto the outside of the container or onto the floor of the production area. One of the problems anticipated with the Lovett apparatus is in the timing of and/or controlling the constant velocity of the transfer cylinder that provides the horizontal movement of the lid press plate. In the Lovett apparatus the transfer cylinder must move a relatively heavy mass. That heavy mass includes at least: the carriage and the pneumatic press cylinder that are attached to the lid press plate. The transfer cylinder and its pneumatic controls are responsive to the pneumatic force in the compressed air pressure that is supplied in the manufacturing environment. Any pressure drop in the compressed air supply or pneumatic control system will effect the constant speed and response of the transfer cylinder by slowing its horizontal velocity. Any variation of the back pressure in the exhaust air control lines will also effect the velocity of the transfer cylinder. Another problem anticipated with the Lovett apparatus is in the matching of the container speed when the velocity of the conveyor may vary due to voltage fluctuations and or frictional loading at any particular time. The Lovett apparatus may require the constant attention and adjustment by an operator. Any constant attention that is required would add to the operating cost of producing the end product. Any spillage would result in product loss and resultant clean up costs and containment that would also add to operating costs.
The present invention addresses the problems identified above by exactly matching the velocity of the lid press plate to the velocity of the container at any time by allowing the container to apply a driving force to the lid press plate. Variations in conveyor speed and/or normal variations in the compressed air pressure have little or no effect on its matching of the velocity.